1. Field of the Invention
The present invention relates generally to Global Positioning System (GPS) receivers, and in particular, to a voltage controlled oscillator (VCO) open loop coarse amplitude control with respect to process and temperature variations.
2. Description of the Related Art
The use of GPS in consumer products has become commonplace. Hand-held devices used for mountaineering, automobile navigation systems, and GPS for use with cellular telephones are just a few examples of consumer products using GPS technology.
As GPS technology is being combined with these devices, the GPS chips are being placed in widely ranging temperature environments. Further, some of the GPS portions are being made on the same semiconductor chip as other portions of the combined devices, which subjects the GPS portions of these electronic devices to widely-varying semiconductor processing steps. Since the GPS portion of the chips are temperature and process dependent, it becomes more difficult to produce a large yield of semiconductor chips with GPS functionality.
One of the temperature and process dependent portions of the GPS functionality is the voltage controlled oscillator that is required for GPS quadrature modulation and demodulation. As the temperature of the chip changes, or the processing across the wafer changes, the output of the VCO signals changes, which introduces errors in the GPS calculations.
Further, because GPS usage has been placed in new products, other issues, such as lower signal strength of the received signals has become an issue.
It can be seen, then, that there is a need in the art for a VCO that can generate signals that are less temperature dependent. It can also be seen that there is a need in the art for a VCO that can generate signals that are less process dependent.